It is known to form nitrodiarylamines from nitrohaloarenes and N-acylaromatic amines or other activated form of the amine in the presence of a so-called acid acceptor for which purpose potassium carbonate is commonly used. For reasons which have not heretofore been explained, sodium carbonate gives inferior results. The process suffers from the disadvantages, among others, that large amounts of inorganic salts are required and large amounts of by-products are formed. The disposal of by-products creates an environmental problem. A process has now been discovered which reduces the amount of inorganic material required, minimizes side reactions and reduces the load on the environment.